Coated abrasive back-up pad



Feb. 6, 1962 D. .1. OLTON 3, 1 ,570

COATED ABRASIVE BACK-UP PAD Filed May 2, 1960 FIG-3 INVENTOR. DIRCK J. OLTON ATTORNEY rate ice

3,019,570 (IOATED ABRASIVE BACK-UP PAD Dirck .I. Qlton, Loudonville, N.Y., assignor to Norton Company, Troy, N.Y., a corporation of Massachusetts Filed May 2, 1960, Ser. No. 25,949 1 Claim. (Cl. 51195) The present invention relates in general to abrading devices and more particularly to a device for holding coated abrasive discs or the like properly centered on a back-up plate of an abrading device.

The conventional method of using coated abrasive discs has been to place a circular abrasive disc on a circular pad and to fasten the disc to the pad by any of a number of centrally located holding devices.

Recently there have been developed coated abrasive discs of a non-circular or at least irregular configuration. These discs are generally used with a back-up pad which has a similar configuration to that of the disc. The most practical of these recently developed non-circular discs has been the disc described and claimed in the copending application of Leland H. Vorce, Serial No. 9,345, filed February 17, 1960.

In its preferred embodiment, this disc has two parallel straight edges, the ends of which are joined with an arcuate edge as illustrated in FIGURE 1 of the drawings. In use, such non-circular discs are mounted on a back-up plate of rubber, steel or the like which conforms in shape to the shape of the disc. Care must be taken to line the disc up with the pad so that the pad is completely covered by the disc. When the central fastening device (usually a nut and washer threaded over a shaft extending through a center hole on the disc and pad) is tightened, the disc frequently becomes misaligned with the pad. Likewise, even with proper alignment, in usage there may be some slippage between the disc and the pad resulting in the undesirable misalignment of pad and disc. When misalignment occurs, the pad is damaged by contact with the workpiece or the disc itself is torn when the unsupported section thereof engages the work.

Accordingly, it is an object of the present invention to provide a means for preventing misalignment of a non circular disc on a back-up pad.

An additional object of the present invention is to provide an improved back-up pad for use with non-circular discs.

Additional objects, if not specifically set "forth herein, will be readily apparent to one skilled in the art from the following detailed description of the invention:

In the drawings:

FIGURE 1 is a plan view of a back-up pad of the present invention with a coated abrasive disc in place thereon and the assembly mounted on a spindle of a power sander.

FIGURE 2 is a plan view of a modified pad.

FIGURE 3 is a side view of the back-up pad of FIG- URE 2.

Generally, the present invention contemplates the provision of positioning projections on the face of the pad, so located and formed as not to interfere with the normal use of the coated abrasive discs mounted upon such pad. More specifically, the invention contemplates the use of one or more relatively flexible projections firmly aflixed to the surface of the pad, said projections having at least a portion thereof extending above the plane of the working surfaces of the pad, to cooperate with an opening in the surface of the coated abrasive disc adapted to be mounted upon such pad so as to fix the position of such disc upon the pad and to aid in retaining the disc in the position so fixed.

Referring now to FIGURE 1 of the drawings, 10 designates the housing of a power sander having a mounting spindle 11 thereon. Mounted on the spindle 11 is a relatively flexible back-up pad (hidden by the superimposed coated abrasive disc) and a coated abrasive disc 12 of a non-circular configuration. The disc 12 is held to the back-up pad by a retaining washer 13 and a central retaining nut 14 threaded upon spindle 11.

Projecting through apertures in the disc 12 are locating projections 15 which are fixedly secured to the pad. These projections are preferably formed of rubber and may be circular, rectangllar or otherwise shaped in cross-section. The projections 15 illustrated in FIGURE 1 are circular in cross-section and are located in close proximity to the center of the disc and pad where they extend upwardly from the Working surfaces of the pad a distance sufficient to project through openings in the surface of the abrasive disc superimposed upon such pad.

FIGURE 2 is a plan view of a modified pad 2!) alone, showing the center hole 21 and the projections 22. In this illustration only two projections are shown and these as rectangular in cross-section rather than circular as in FIGURE 1. Pad 20 is shown as having a depressed center portion 23a common expedient in many coated abrasive back-up pads. The projections 22 have a portion 24 there-- of which extends above the plane of the working surfaces 25 of the pad. By the term working surfaces is meant that portion of the back-up pad which is in contact with the abrasive disc mounted thereon at a point immediately below or closely adjacent the portion of the abrasive disc which contacts the workpiece to be abraded. It is within the scope of the present invention to utilize any number of such projections, the objects of the invention being achieved so long as at least one projection is provided.

FIGURE 3 is a side view of the pad of FIGURE 2 illustrating the manner in which the projections 22 extend up from the surface of the pad 20.

The projections on the pad of the present invention are preferably moulded into the pad when it is formed (if made of rubber, plastic or the like) but could obviously be adhered to the surface of an existing pad by any suitable adhesive or mechanical fastening means if desired.

I claim:

A non-circular back-up pad for coated abrasive discs of similar configuration to the pad comprising a flexible, relatively planar member; means on said member to secure the same to the shaft of a rotary tool; and means to positively locate and hold the abrasive disc on said member in direct alignment with said member, said last-mentioned means comprising at least one relatively flexible projection extending outwardly from the surface of said member.

References Cited in the file of this patent UNITED STATES PATENTS 1,928,800 Stever Oct. 3, 1,933 

